Rheostat



(No Model.) 2 Sheets-Sheet l.

R. H. MATHER.

RHBOSTAT.

No. 347,120. Patented Aug. 10, 1886.

(No Model.) R- H' MATHER. 2 Sheets-Sleet 2.

RHBOSTAT. No. 347,120. Patented Aug. 10,1886.

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UNITED STATES PATENT RICHARD H. WIATHER, 0F VINDSOR, CGNNECIICUT.

RH EOSTA'E".

SPECIFICATION forming part of Letters Patent No. 347,120, dated August 10,1886,

Application tiled February 17, 1856. Serial No. ifljil.

To all whom it may concern:

3e it known that I, Iticnnnn II. hInfrnER, a citizen of the United States, residing at lVindsor, in the county of Hartford and State of Connecticut, have invented certain new and useful Improvements in Rheostats, of which the following is a specification, reference being had to accompanying drawings.

My invention relates to instruments for the measurxnent of electric currents by the method of comparison with known resistances, and particularly to mechanism by means of which resistance-coils may be introduced into an electric-circuit7 and the resistance so introduced may be read from the face of the instrument introducing the same.

The object of my invention is to combine a set of resistancecoils, and an indexplate or face-plate, indicating the absolute resistance of such coils, with convenient mechanism for the manipulation of said coils, in such a inanner that the resistance introduced at any time into an electric circuit by the use of my iinproved rheostat shall be correctly indicated by the igure or iigures then visible by the observer, while all other index-iigures shall be hidden from view. rIhis object I accomplish by means of the electrical and mechanical devices which are illustrated inthe accompanying drawings.

Figure lin the drawings is a top view of my improved rheostat. Fig. 2 is a top view ofthe same, a part being removed. Fig. 3 is a longitudinal section of Fig. l. Fig. 4 is a detail. Fig. 5 is a bottom view of said rheostat. Fig. 6 is a detail showing resistancecoils, spools, and connections.

In the drawings, A is an indexplate of hard rubber, preferably of circular form, and is of sufficient thickness to allow the contiguous parts of the instrument to be conveniently and iirmly attached thereto in the manner which is hereinafter described. In the middle of this plate and extending through its entire thickness is a hole, which is occupied by a brass stud, B, whose head C is countersunk in the top of plate A. The lower eX tremity of stud I3, protruding from plate A, is a screw, and is provided with a brass nut, I), by means of which the stud B is held irnmovably iu position in plate A. Nut D is electrically connected with a bindingpost,

(No model.)

which forms the positive terminal of the instrument, but is not shown in the drawings. Stud B is also provided with a stem, E, which passes up through the cap-plate O, hereinat ter mentioned, and is provided with a termi nal washer, F, and with a screw, G, which holds the latter in position. A circumferential iiange or shoulder, II, is formed at the periphery of plate A, whereby ihe latter may be conveniently iitted into the top of a wooden box, wherein the resistance coils are located. This box is not shown in the drawings. Plate A has ten other perforations, which are equidistant from each other, and equidistant from the center of the plate A. rilhe distances here involved are such as to allow convenient room for the adjustment of the resistance-coil spools and for the application of the cap-plate, in the manner hereinafter mentioned. Each oi" these perforations is occupied by abrass stud, J, which is provided with a head, countersunk in the top of plate A. The several heads of studs J are respectively indicated in the drawings by the index-iigures 0, l, 2, 3, Ll, 5, 6, 7, 8, and 9. rEhe same gures are stamped or engraved upon the upper surfaces of the same stud-heads, as exhibited in Fig. 2. Each stud J, excepting one, (see stud No. 9,) is provided with a terminal screw, Il, protruding below'plate A.

Mis a stop consisting of one or more pins rising from the upper surface of plate A in the position hereinafter indicated.

G is a circular cap-plate of hard rubber, and by a central perforation is mounted rotatably upon stem E of stud' I3,where it is held snugly against the top of plate A by means of washer F and screw 'd Ilate C has a peripheral finger-piece, I), extending radially therefrom in position to engage stop M. Plate O is pierced near its outer edge by a sight-hole, Q, of conveuientsize and position to allow an observer, by looking through hole Q., to read the index-figures above mentioned, but not large enough to expose any two such readings at one and the same time. Said stop M, hole Q, and finger-piece l? arc so located relatively to each other that cap-plate O, when rotated to its full extent, is stopped in one direction in position to show theindexhgure 0, as in Fig. l, and in the other direction to show the index-figure 9. The under surface of capplate Ois cut away in a radialchannel from hole Q to the middle of plate O. This channel, which is shown in Figs. 3 and 4, is of sufficient size to accommodate spring S. The latter, being formed of brass and movable' within said channel, is held in positionby screw B,andis terminally at all times in pressing contact with the stemE of stud B and with the upper surface ofv plate A, including the upper surfaces of the index-numberedhead's of studs J. The width of spring S at its outer extremity is greaterthan/the distance between any two adjacent studs J. Abrass spool T, provided with a terminal female screw, is firmly screwed upon each of the terminal screws L. The spools T are of uniform size and shape for the accommodation of resistance-coils of the desired resistance. Such a coil, U, of insulated German-silver wire, is wound upon each spool T in the usual manner, being doubled before winding, in order to prevent magnetization by induction. These coils and spools, the latter being arranged in the relative positions shown in Fig. 5, are connected with each other in the following manner: One end of each coil is soldered to the lower part of the spool upon which it is wound, as shown in Fig. 6, and the other end of the same coil, except in the case of the coil upon the last spool, is soldered to the lower part of thespool whose stud bears the next -higher index-number; and the last coil since there is no spool attached to the stud of index-number 9, is soldered directly to that stud. The first of said spools or studs, indexnumber 0, isconnected with a binding-post,

(not shown in the drawings,) which constitutes the negative terminal ofthe instrument. The positive and negative terminals of the instrument are sufficiently indicated in Fig. 3 by the signs -land-, respectively.

The figures l0 which are marked upon the instrument and are reproduced upon the indexplate in Figs. l and .2 indicate the number ofohms of resistance in a single coil U.

In constructing a series of rheostats for general use it is convenient to employ in successive instruments coils whose resistances are successive decimal multiples or sub-multiples of the standard ohm.

It is obvious that the index-numbers, instead of being stamped upon the studs J, may be marked upon any other convenient part ofy the upper surface of the index-plate A, provided that the above-described relative location of the finger-piece I), stop M, and hole Q be still preserved.

` Such being the construction of my improved rheostat, the mode of its operation is as follows: Starting with the index-figure 0 in view, the instrument is placed in any electric circuit into which it is desired to introduce any known resistance within the capacity of the instrument. By means of the Enger-piece P the cap-plate O is then turned until the number indicating the desired resistance is visible upon plate A through hole Q. When the rheoy stat is at the zeropoint, as shown in Fig. 1, the

electric' current passes between the terminals of the instrument by the way of nut D, stud B, spring S, stud 0, and the spool which is 7o attached to stud 0. No resistance-coil is then in circuit. When' the cap-plate is turned so as to disclose index No. 1, the spring passes from its position of contact with stud No. 0 across the intervening space to a position of contact with stud No. l, and then the current passes from the positive terminal through the nut D, stud B, spring S, spool under stud No. 1, and resistance-coil under stud No. 0 to the negative terminal; and so, if it is desired to introduce another resistance-coil, thc cap-plate is further turned until index figure 2 is visible through the cap-plate.v The current then passes through the first and second resistancecoils and through the spool and stud No. 2. In the same way the instrument is further operated for greater resistances up to its full capacity. By means of a series of rheostats of j the same general description,l but of different resistances, it is possible to introduce into the circuit any resistance which may be desired.

This rheostat possesses an advantage over other rheostats now in use, byreason of the circumstance that the resistance introducedan opening which is at all times directly over any such st'ud with which said spring is for the time being in contact, substantially in the manner and for the purpose specied.

2. A rheostat consisting of several resistance-coils electricallyv connected in series and provided with numbered contact-studs in an index-plate, in combination with a cap-plate which is mounted rotatably upon such indexplate,` is provided with a sliding contact, and has an opening which is always found directly over a predetermined number or other mark indicating the resistance of the rheostat in the position in which it is for the time being adjusted, substantially in the manner and for the purpose specified.

IOO

IIO

3. A'rheostat consisting of a number of rex2 5 ber or other character marked upon the face of such index-plate and indicating the aggregate resistance of those resistance-coils which are for the time being in circuit, substautialy I spring, substantially n the manner and for 1o in the manner :md for the purpose speeied. the purpose speeed.

4. A rheostat Consisting of a number of re- In witness whereof I have hereunto Set my sstauCe-ools in series, and a corresponding name in the presence of two Witnesses. number of contact-Surfaces aud index-characters on the face of au index-plate, in oomb- RICHARD H' MATHER' nation with a cap-plate which is mounted rota- VTitueSses: tably upon said index-plate, and is provided ALBERT H. XVLKER,

with a sight-hole and circuit-closing contact- VILLARD EDDY. 

